He was initially transported to Roosevelt Hospital in New York after the fight for treatment on his hands and nose, according to ESPN.com. The blood clot was discovered when doctors did an examination on him after his arrival, said Nathan Lewkowicz, vice president of Sampson Boxing.

"He was taken to the hospital to make sure he was OK and once he was there they found (the clot)," Lewkowicz said. "He thought he broke his left hand in the second round and also thought he had broken his nose at some point in the fight. But the bigger concern once he was at the hospital was the head injury they discovered."

Newsday reported that Abdusalamov's face was bloodied and his left cheekbone severely swollen after the fight. He had scored 18 straight knockouts coming into the bout against Perez, per Newsday. ()

Abdusalamov, 32, (18-1, 18 KOs) remained in hospital and listed in stable condition, according to ESPN.com.

"He had surgery to have the blood clot taken out and a small piece of his skull removed to allow the [brain] swelling to go down," Lewkowicz told ESPN.com. "After the fight he seemed fine, but they took him to the hospital to check him out and because he wasn't feeling so good."

HBO Sports president Ken Hershman issued a statement on the HBO's website, saying that the network will speak more extensively as Abdusalamov improves.

"The thoughts and prayers of all of us at HBO Sports are with Magomed Abdusalamov," Hershman said in the statement. "We are grateful for the medical care he is receiving here in New York City and out of respect for Magomed and his family, we will wait for any official updates on his condition before making any further statements."